Chaplet coating



Patented May 9, 1950 CHAPLET COATING Harold Barnes Underwood, Detroit, Mich., aa-

slgnor to Ford Motor Company, Dearborn, Mich., a corporation of Delaware No Drawing. Application June 19, 1948,

Serial No. 34,139

Claims. 1

This application is concerned with the founding art and more particularly with that portion of the foundry art which relates to the preparation of molds and cores.

It has long been the practice in the foundry art to use metal devices called chaplets to reinforce sand cores and molds and to secure the various parts of such molds and cores together when they are assembled from more than one individual part. It has also long been the practice in the founding art to give a smooth finish to molds and cores by means of applying to the surface thereof a preparation known generally as "core washes. These core washes differ widely in specific composition, but are practically all based upon a suspension of silica flour in water. Graphite is often added to such a composition. These core washes thus contain two very refractory substances and help to prevent the sand of the core or mold from burning into the metal as well as giving a better finish to the casting.

The chaplets employed in the ferrous founding field are usually made from low carbon steel because of its cheapness and ease of fabrication. It is a frequent occurrence in the foundry industry that castings are so designed that at certain locations the chaplets are in direct contact with the molten iron when the mold or core is poured. and in which it is essential that the chaplet fuse into and become an integral part of the finshed casting. In pouring castings from gray iron, the pouring temperature is usually several hundred degrees lower than the melting point of the mild steel chaplets. Thus it is impossible for the heat of the poured metal to immediately fuse the chaplets and permit them to dissolve in the mass. The assimilation of mild steel chaplets into a gray iron casting must take place by diffusion rather than by a direct melting.

This fact has caused trouble in locations where it has been found necessary to use a refractory core wash on a gray iron casting mold which must come into direct contact with the mild steel chaplets. The core wash will not drain completely from the chaplets and hence when the core or mold is poured, a layer of refractory core wash is interposed between the molten gray iron and the steel chaplets. This layer of refractory wash is thin, but it is often sufiicient to prevent diffusion of the steel chaplet into the gray iron mass thoroughly. The result is a defective casting that can be reclaimed only by a welding procedure.

In an effort to overcome this difilcult, the chaplets have been cleaned by hand before pouring,

but this has been a costly and undependable operation. The application of various substances to the chaplet surface after assembly of the core or mold and prior to the application of the core wash has been tried with at best indifferent and inconclusive results. Among the substances which have been so tried are kerosene, Vaseline, light mineral oil and polyvinyl alcohol.

The difficulties described above have been practically solved by the simple expedient of coating the chaplets after they have been assembled in the mold or core and prior to the application of the core wash with the class of compounds known technically as polyorganosiloxanes or more commonly as silicones. It is preferred to use those members of this class of compound which display a viscosity suitable for application as a spray through a conventional spray gun. However, this is not essential and the silicone can be applied by brushing or in any desired manner capable of depositing a thin, uniform coating over the exposed surface of the chaplet. Chaplets so coated do not retain any of the core wash but drain cleanly. Thus the molten gray iron impinges upon a clean chaplet surface and the chaplet diffuses into the gray iron before the solidification temperature is reached.

It is preferred to employ for this purpose a product having a viscosity of about 350 centistokes. However, any other of the commercially available silicones having a comparable viscosity can be employed. While a preparation having a viscosity in the neighborhood of 350 centistokes is preferred, other preparations having viscosities of 100, 200, and 500 centistokes have been successfully used. When using the preparation having the viscosity of 350 centistokes, one pound of the silicone is capable of coating about 6,000 chaplets.

The silicone should be employed undiluted as all attempts to dilute this material prior to use have given unsatisfactory results. As little as one part of kerosene mixed with three parts of silicone gives unsatisfactory results in that the core wash drains from the sprayed chaplets only incompletely.

While the above description depicts a process in which the silicone material is applied to the chaplets after they have been placed in the mold or core, it is to be understood that the invention also includes the coating of the chaplets at any time prior to the application of the core wash. For example, the chaplets can be coated with silicone and then incorporated into the mold or 0011!.

'Iheadoptionofthisprocessinacommercial foimdry has been found to reduce the amount of castings required to be welded to about onehalf of those previously welded.

I claim as my invention:

1. In the preparation of foundry molds or cores. the steps of coating the exposed surfaces of metal chaplets with a polyorganosiloxane compound and then applying to the coated chaplets a core wash 2. In the preparation of foundry molds or cores in which chaplets are employed and which chaplets are located so that they are exposed to the action of molten metal when the mold or core is poured, the steps of coating said chaplets with a poly rsanosiloxane compound and then applying to the coated chaplets a core wash.

3. In the preparation of foundry molds or cores in which chaplets are employed and which chaplets are located so that they are exposed to the action of molten metal when the mold or core is poured, the steps of coating the chaplets with a polyorganoslloxane compound having a viscosity of between 100 and 500 centistokes and then applying to the coated chaplets a core wash.

4. In the preparation of foundry molds or cores 4 in which chapletsareemployed andwhich chaplebarelocatedsothattheyareexposedtothe 1 action of molten metal when the mold or core is REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,589,881 Spencer June 2, 1925 1,687,799 Shimer Oct. 18, 1929 2,258,218 Rochow Oct. '1, 1941 OTHER REFERENCES "Plastics" of Chicago, Ill., January 1945. mes 40, 42, 44, 112-115.

Silicone Resins in Protective and Decorative Coatings pages 439-442. 

1. IN THE PREPARATION OF FOUNDRY MOLDS OR CORES, THE STEPS OF COATING THE EXPOSED SURFACES OF METAL CHAPLETS WITH A POLYORGANOSILOXANE COMPOUND AND THEN APPLYING TO THE COATED CHAPLETS A CORE WASH. 